Metallocene catalysts are of great interest in the industry because of the great opportunity they provide for tailoring polymer products. Thus there is a need in the art to provide new and varied metallocene catalysts that can produce new and/or tailored polyolefins.
Along this vein, scientists have tried unusual bridging groups looking to find even more interesting catalysts. One such bridging group was diphenyl germanium, which was used as part of diphenyl germanyl flucrenyl cyclopentadienyl zirconium dichloride and methylalumoxane catalyst system, (K. Patsidis et al, Journal of Organometallic Chemistry 509 (1996) 63-71). Patsidis reported that the germanium bridge produced higher molecular weight polypropylene as compared to analogous silica systems.
Hermann et al, (Journal of Organometallic Chemistry 509 (1996) 115-117) disclose the polymerization of ethylene using tin bridged zirconocene in combination with methyl alumoxane. (see also related EP 742 225 A1.) U.S. Pat. No. 5,631,335 also discloses tin bridges.
Riken Review No. 15, August 1997, page 17-18, (The Institute of Physical and Chemical Research) discloses that germanyl bridged zirconocene and hafnocene-MAO catalysts produced higher molecular weight and isotactic polyhexene.
EP 0 316 155 discloses polymerization of propylene using methylalumoxane and dimethylgermylbis(methylcyclopentadienyl)zirconium dichloride.
U.S. Pat. No. 5,532,396 discloses the production of a propylene-ethylene copolymer using rac-diethylgermyl(2-methyl-4-phenyl-1-indenyl)(2-ethyl-1-indenyl)zirconium dichloride combined with methylalumoxane. However, Table I appears to disclose ethylene polymerization using rac-diethylgermyl(2-methyl-4-phenyl-1-indenyl)(2-methyl-1-indenyl)zirconiu m dichloride or rac-diethylgermyl(2-methyl-4-[1-napthyl]-1-indenyl)(indenyl)zirconium dichloride both with MAO. Since the catalyst activity is reported as PP/g metallocene x hr and example 1 (which Examples 25-28 repeated) used propylene, it is assumed that monomer polymerized was propylene, not ethylene.
U.S. Pat. No. 5,081,322 discloses the production of a polypropylene wax (having about 2.9 weight % ethylene comonomer) using dimethylgermylbisindenylzirconium dichloride combined with methylalumioxane.
Rac(dimethylgermylbisindenylzirconiumdichloride combined with MAO is disclosed as a polymerization catalyst for propylene in W. Spaleck, et al, New Journal of Chemistry, volume 14, number 6/7 June/July/1990, page 499-503.
U.S. Pat. No. 5,696,045 discloses a mixture of dimethylsilylbis(2-methyl-4,6-diisopropyl-1-indenyl)zirconium dichloride and dimethylgermanylbisindenylzirconiumdichloride combined with MAO as a propylene polymerization and copolymerization catalyst. (ethylene is disclosed as comonomer.)
EP 553 757 discloses polymerization of propylene using rac(dimethylgermanylbisindenylzirconiumdichloride in combination with methylalumoxane.
U.S. Pat. No. 5,350,817 discloses the polymerization of propylene with mixtures of zirconocenes including rac dimethylgermylbisindenyl zirconiumdichloride combined with MAO.
EP 480 390 also discloses the production of polypropylene using dimethylgermanylbisindenylzirconiumdichloride combined with MAO.